Add sheriff documentation for rebaselining.

site/dev/sheriffing/index.md

 Tree Sheriffs Documentation
 ===========================
 
 ### Contents ###
 
 *   [What does a sheriff do?](#what_is_a_sheriff)
     +   [Skia tree](#skia_tree)
     +   [DEPS rolls](#deps_rolls)
     +   [Gold and Perf](#gold_and_perf)
     +   [Documentation](#sheriff_doc)
 *   [View current and upcoming sheriffs](#view_current_upcoming_sheriffs)
 *   [How to swap sheriff shifts](#how_to_swap)
 *   [Tips for sheriffs](#tips)
     +   [When to file bugs](#when_to_file_bugs)
     +   [How to close or re-open the tree](#how_close_tree)
     +   [Compile bot failures automatically close the tree](#tree_closers)
     +   [How to revert a CL](#how_to_revert)
     +   [What to do if DEPS roll fails to land](#deps_roll_failures)

[rmistry, 2015/04/03 14:54:33]

Also add a link here to your new section.

[scroggo, 2015/04/06 17:44:52]

Done.

 
 
 <a name="what_is_a_sheriff"></a>
 What does a sheriff do?
 -----------------------
 
 A sheriff keeps an eye on the tree, DEPS rolls, Gold tool and the Perf tool.
 
 Below is a brief summary of what the sheriff does for each task:
 
@@ skipping 76 matching lines @@
 <a name="how_to_revert"></a>
 ### How to revert a CL
 
 See the revert documentation [here](https://skia.org/dev/contrib/revert).
 
 
 <a name="deps_roll_failures"></a>
 ### What to do if DEPS roll fails to land
 
 A common cause of DEPS roll failures are layout tests. Find the offending Skia CL by examining the commit hash range in the DEPS roll and revert (or talk to the commit author if they are available). If you do revert then keep an eye on the next DEPS roll to make sure it succeeds.
+
+<a name="how_to_rebaseline"</a>
+### Rebaseline Layout Tests (i.e., add suppressions)

[rmistry, 2015/04/03 14:54:33]

When would the sheriff need to do this?
Maybe you can add a line in the above section ("What to do if DEPS roll fails to
land") explaining when this would need to happen and link to this new section.

[scroggo, 2015/04/06 17:44:52]

Done.

+
+1. First create a Chromium bug:
+ * goto crbug.com

[rmistry, 2015/04/03 14:54:33]

Making this a link might be useful.

[scroggo, 2015/04/06 17:44:53]

Done.

+ * Make sure you’re logged in with your Chromium credentials
+ * Click “New Issue”
+ * Summary: “Skia image rebaseline”
+ * Description:
+  * DEPS roll #,

[scroggo, 2015/04/03 13:43:13]

I was trying to indent this further, but did not know how. Is there
documentation how to generate the documentation somewhere?

[rmistry, 2015/04/03 14:54:33]

The documentation is here: https://skia.org/dev/tools/markdown
but I do not see anything about indenting it. I think what had worked for me was
indenting by two spaces, if that does not work then try to do it how the first
Contents section does it.

[jcgregorio, 2015/04/06 17:57:21]

Yes, it is two spaces, see the nested list on this page:

 https://skia.org/dev/tools/markdown.md

[scroggo, 2015/04/06 18:01:44]

Yeah, that's the page I'm looking at, and my latest CL I *think* I'm doing the
same thing, but it does not appear to be working.

+  * helpful message about what went wrong (e.g., “Changes to how lighting is scaled in Skia r#### changed the following images:”)

[rmistry, 2015/04/03 14:54:34]

Nit: helpful -> Helpful

[scroggo, 2015/04/06 17:44:53]

Done.

+  * layout tests effected

[rmistry, 2015/04/03 14:54:33]

Nit: layout -> Layout

[scroggo, 2015/04/06 17:44:52]

Done.

+  * You should copy the list of affected from stdio of the failing bot
+ * Status: Assigned
+ * Owner: fmalita@
+ * cc: reed@, bsalomon@, robertphillips@ & developer responsible for changes
+ * Labels: OS-All & Cr-Blink-LayoutTests
+ * If it is filter related, cc senorblanco@
+
+2. Edit skia/skia_test_expectations.txt

[rmistry, 2015/04/03 14:54:34]

A link to the file in googlesource might be useful.

[scroggo, 2015/04/06 17:44:52]

Done.

+ * Add # comment about what has changed (I usually paraphrase the crbug text)
+ * Add line(s) like after the comment:
+  * crbug.com/<bug#youjustcreated> foo/bar/test-name.html [ ImageOnlyFailure ]
+
+3. Commit the changes and fire off new try bots (you usually only need to fire off the layout bots)